With the development of the mobile Internet and popularization of intelligent terminals, an amount of data in a network sharply increases. To efficiently process the data, a wireless local area network (wireless local area network, WLAN) system that has advantages such as a high rate and low costs becomes one of mainstream mobile broadband access technologies.
To further increase a service data transmission rate of the WLAN system, in the Institute of Electrical and Electronics Engineers (Institute of Electrical and Electronics Engineers, IEEE) 802.11n/ac standard, several adjacent channels (for example, a bandwidth of each channel is 20 MHz) are merged into a channel that has a larger bandwidth (for example, 80 MHz or 160 MHz), and then service data transmission is performed by using this channel that has a larger bandwidth. In this way, the service data transmission rate of the WLAN system is exponentially increased. In addition, with the continuous development of the mobile Internet, more unlicensed spectrums are applied to the WLAN system. For example, the Federal Communications Commission (Federal Communications Commission, FCC) will release 195 MHz of 5 GHz spectrums for use in the WLAN system, that is, in the future, a capability of supporting multiple channels by the WLAN system will be further improved. In a WLAN system having multiple channels, because a station (Station, STA) does not know which subchannel among multiple subchannels of the WLAN system is a primary channel (the primary channel includes a beacon frame required for accessing a network by the STA), in order to access the network, the STA needs to perform scanning on the multiple subchannels. To ensure that a STA can fast access a network, in the prior art, an access point (Access Point, AP) needs to send a beacon frame on each available subchannel, so that the STA fast acquires the beacon frame by scanning the subchannel, and further obtains, from the beacon frame, information required for accessing the network, so as to achieve access to the network.
The prior art has at least the following problem: In the prior art, an information length of a beacon frame is large (for example, an information length, specified in the IEEE 802.11b standard, of a beacon frame is approximately 160 bytes); in this case, in a WLAN system having multiple channels, if an AP sends a beacon frame on all available subchannels in order for a STA to perform scanning and access, large network overheads are brought to the WLAN system.